By Dan Levine and Robin Respaut

SAN FRANCISCO, Feb 17 (Reuters) -

The state of California is preparing a lawsuit challenging recent federal changes to U.S. childhood vaccine recommendations made by the Trump administration, the state's attorney general said in an interview on Tuesday.

Rob Bonta, the attorney general of the most populous U.S. state, also said he would "maybe" be open to working with the Trump administration and U.S. Health and Human Services Secretary Robert F. Kennedy Jr. to limit broad federal immunity for drug companies over alleged vaccine injuries.

HHS did not immediately respond to a request for comment.

A California lawsuit over the childhood vaccination schedule would add legal pressure on the administration, as medical organizations and public health experts have warned the changes could lower vaccination rates.

Kennedy has upended longstanding vaccine policies since his taking office last year. The Centers for Disease Control and Prevention has issued a new immunization schedule that removed universal recommendations for vaccines against rotavirus, influenza, meningococcal disease, hepatitis A and hepatitis B, stating that parents should consult with healthcare providers under what it calls shared clinical decision-making.

The American Academy of Pediatrics $(AAP)$ and other leading medical organizations have sued in a bid to stop the new vaccine schedule, arguing the overhaul was illegal and not driven by evidence. The suit seeks to replace the Kennedy-appointed Advisory Committee on Immunization Practices and have its decisions overturned.

In an interview with Reuters on Tuesday, Bonta and Connecticut Attorney General William Tong both expressed disdain for Kennedy's views on vaccines. In terms of new litigation, Bonta said his "team is mobilized" and is "looking at what the complaint looks like, where to file, what our standing is, all the, all the things we have to have locked in."

Bonta did not provide additional details about the planned lawsuit, including when it would be filed. Tong also said "we're scrambling our jets," and a spokesman for his office later confirmed that it is working with California on a potential multistate filing.

When it comes to vaccine injuries, U.S. law mandates that most people seeking to sue drug manufacturers file their claims with a special vaccine court run by HHS that aims to address claims quickly, while capping compensation and limiting liability for the companies.

The program has long been targeted by Kennedy and his allies, in part because HHS defends those cases, rather than pharma companies themselves. Before leading HHS, Kennedy represented plaintiffs claiming vaccine injuries and played an instrumental role in organizing mass litigation against drugmaker Merck MRK.N over its Gardasil vaccine. A U.S.judge ruled for Merck in many of those cases.

Bonta expressed skepticism towards broad immunities conferred by Congress to specific corporate sectors, including vaccine makers, but he said he did not want to feed anti-vaccine views espoused by Kennedy.

"I like the facts. I like science. I don't want to give any airtime to his-- I mean, just conspiracy bullshit," Bonta said.

"Can there be an example of a pharmaceutical company that did something wrong, and hurt people based on the facts, and they're enjoying absolute immunity when they should have accountability? Yeah, that's possible," Bonta added.

(Reporting by Dan Levine and Robin Respaut in San Francisco; editing by Peter Henderson and Ethan Smith)